1. Field of the Invention
The present invention relates to a distance correction method and the controller for the reflectometer which measures the Fresnel reflection and Rayleigh back-scattering light of an optical fiber or an optical waveguide.
This application is based on patent application No. Hei 09-142766 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
A conventional light signal propagating apparatus utilizing the difference in the specific refraction ratio, for example, an optical fiber or quartz optical waveguide, requires its resulting distance to be corrected with the formula (1): EQU D.sub.wg =D.sub.v /n (1)
when measuring the Fresnel reflection or Rayleigh back-scattering light by reflectometer because the propagation speed of the light signal in the above apparatus is slower than in a vacuum or in air. Here, D.sub.wg is a length of the light signal propagating apparatus to be tested, D.sub.v is a distance measured by the reflectometer, and n is a group refraction ratio of the above light signal propagating apparatus.
A light transfer method with a large capacity such as the time sharing multiple light transfer method or the light wavelength multiple transfer method requires the dispersion compensation management with a dispersion compensator set on a dispersion compensation optical fiber or a quartz board, because transfer characteristics are considerably degraded due to dispersion by the light propagation apparatus, such as an optical fiber. Consequently, light signal propagation apparatuses which have different group refraction ratio are connected in a series.
Also, a light composite module is mostly an assembly of the components which have a different refraction ratio such as a light signal propagation apparatus, for example, an optical fiber, lens or prism. There is often air between those above components.
There is a problem in the conventional distance correction method using reflectometer, in which the above components or light signal propagation apparatuses with different refraction ratios are connected in series, making accurate correction difficult because the correction is performed as a whole.